In vehicle industry field of recent years, there is a development of a system disclosed in patent document identified below, i.e., a so-called electromagnetic suspension system (hereinafter abbreviated to as “electromagnetic suspension” where appropriate) in which an electromagnetic actuator is arranged to function as a shock absorber (damper). This electromagnetic suspension is expected as high-performance suspension system, owing to its advantages such as easy establishment of suspension characteristic based on a so-called skyhook theory.    [Patent Document 1] JP2002-311452A